Ensemble Feedback Stabilization of Linear Systems

Stabilization of linear control systems with parameter-dependent system matrices is investigated. A Riccati based feedback mechanism is proposed and analyzed. It is constructed by means of an ensemble of parameters from a training set. This single feedback stabilizes all systems of the training set and also systems in its vicinity. Moreover its suboptimality with respect to optimal feedback for each single parameter from the training set can be quantified

Influence of a Thermo-Mechanical Treatment on the Fatigue Lifetime and Crack Initiation Behavior of a Quenched and Tempered Steel

A thermo-mechanical treatment (TMT) at the temperature of maximum dynamic strain aging has been optimized and performed on quenched and tempered steel SAE4140H (German designation: 42CrMo4) in order to improve the fatigue limit in the high cycle fatigue (HCF) and and very high cycle fatigue (VHCF) regimes. Fatigue tests, with ultimate cycle numbers of 107 and 109, have shown that the TMT can increase both the fatigue lifetime and the fatigue limit in the HCF and VHCF regimes. The increased stress intensity factors of the critical inclusions after the TMT indicate that the effect can be attributed to a stabilized microstructure around critical crack-initiating inclusions through the locking of edge dislocations by carbon atoms during the TM

Intracortical Remodeling Parameters Are Associated With Measures of Bone Robustness

Prior work identified a novel association between bone robustness and porosity, which may be part of a broader interaction whereby the skeletal system compensates for the natural variation in robustness (bone width relative to length) by modulating tissue‐level mechanical properties to increase stiffness of slender bones and to reduce mass of robust bones. To further understand this association, we tested the hypothesis that the relationship between robustness and porosity is mediated through intracortical, BMU‐based (basic multicellular unit) remodeling. We quantified cortical porosity, mineralization, and histomorphometry at two sites (38% and 66% of the length) in human cadaveric tibiae. We found significant correlations between robustness and several histomorphometric variables (e.g., % secondary tissue [R 2  = 0.68, P  < 0.004], total osteon area [R 2  = 0.42, P  < 0.04]) at the 66% site. Although these associations were weaker at the 38% site, significant correlations between histological variables were identified between the two sites indicating that both respond to the same global effects and demonstrate a similar character at the whole bone level. Thus, robust bones tended to have larger and more numerous osteons with less infilling, resulting in bigger pores and more secondary bone area. These results suggest that local regulation of BMU‐based remodeling may be further modulated by a global signal associated with robustness, such that remodeling is suppressed in slender bones but not in robust bones. Elucidating this mechanism further is crucial for better understanding the complex adaptive nature of the skeleton, and how interindividual variation in remodeling differentially impacts skeletal aging and an individuals' potential response to prophylactic treatments. Anat Rec, 297:1817–1828, 2014. © 2014 Wiley Periodicals, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108629/1/ar22962.pd

Anharmonic Evolution of the Cosmic Axion Density Spectrum

We present analytic solutions to the spatially homogeneous axion field equation, using a model potential which strongly resembles the standard anharmonic $(1-\cos N\theta)$ potential, but contains only a piece-wise second order term. Our exactly soluble model for $\theta(t)$ spans the entire range $[-\pi/N,\pi/N]$. In particular, we are able to confirm (i) Turner's numeric correction factors \cite{Turner} to the adiabatic and harmonic analytic treatments of homogeneous axion oscillations, and (ii) Lyth's estimate \cite{Lyth} valid near the metastable misalignment angle $\pi/N$ at the peak of the potential. We compute the enhancement of axion density fluctuations that occurs when the axion mass becomes significant at $T\sim 1$ GeV. We find that the anharmonicity amplifies density \mbox{f}luctuations, but only significantly for relatively large initial misalignment angles. The enhancement factor is $\sim$ (2,3,4,13) for $\theta_{\rm in}\sim (0.85,0.90,0.95,0.99)\times\pi$.Comment: 26 pages, 6 figures appended as a ps-file, Latex, DAMTP-94-21, VAND-TH-94-

Screening and brief interventions for hazardous and harmful alcohol use among patients with active tuberculosis attending primary care clinics in South Africa: a cluster randomized controlled trial protocol

<p>Abstract</p> <p>Background</p> <p>In 2008 the World Health Organization (WHO) reported that South Africa had the highest tuberculosis (TB) incidence in the world. This high incidence rate is linked to a number of factors, including HIV co-infection and alcohol use disorders. The diagnosis and treatment package for TB and HIV co-infection is relatively well established in South Africa. However, because alcohol use disorders may present more insidiously, making it difficult to diagnose, those patients with active TB and misusing alcohol are not easily cured from TB. With this in mind, the primary purpose of this cluster randomized controlled trial is to provide screening for alcohol misuse and to test the efficacy of brief interventions in reducing alcohol intake in those patients with active TB found to be misusing alcohol in primary health care clinics in three provinces in South Africa.</p> <p>Methods/Design</p> <p>Within each of the three selected health districts with the highest TB burden in South Africa, 14 primary health care clinics with the highest TB caseloads will be selected. Those agreeing to participate will be stratified according to TB treatment caseload and the type of facility (clinic or community health centre). Within strata from 14 primary care facilities, 7 will be randomly selected into intervention and 7 to control study clinics (42 clinics, 21 intervention clinics and 21 control clinics). At the clinic level systematic sampling will be used to recruit newly diagnosed TB patients. Those consenting will be screened for alcohol misuse using the AUDIT. Patients who screen positive for alcohol misuse over a 6-month period will be given either a brief intervention based on the Information-Motivation-Behavioural Skills (IMB) Model or an alcohol use health education leaflet.</p> <p>A total sample size of 520 is expected.</p> <p>Discussion</p> <p>The trial will evaluate the impact of alcohol screening and brief interventions for patients with active TB in primary care settings in South Africa. The findings will impact public health and will enable the health ministry to formulate policy related to comprehensive treatment for TB and alcohol misuse, which will result in reduction in alcohol use and ultimately improve the TB cure rates.</p> <p>Trial registration number</p> <p>PACTR: <a href="http://apps.who.int/trialsearch/trial.aspx?trialid=PACTR201105000297151">PACTR201105000297151</a></p

Suitability of pit colliery shale as construction material for unbound base courses

"Grubenberge" fallen beim Auffahren von untertägigen Strecken zur Erschließung von Steinkohlenflözen an. Aufgrund früherer Untersuchungen wurden höhere Anteile an festen Sandsteinen, neben Schluff- und Tonsteinen, erwartet, als in den "Waschbergen" aus dem unmittelbaren Flözbereich enthalten sind. Wegen dieses Sandsteinanteils wurde die Verwendbarkeit der Grubenberge in Tragschichten ohne Bindemittel untersucht. Dazu wurden Frostbeständigkeit, die Raumbeständigkeit und die mechanische Festigkeit von Mineralstoffkörnungen für den Straßenbau geprüft, die in zwei Pilotanlagen aus Grubenbergen aufbereitet wurden. Die Untersuchungen ergaben, dass sowohl die Widerstandsfähigkeit gegen Frost als auch die Raumbeständigkeit der Grubenberge nicht den geltenden Anforderungen an Mineralstoffe für den Straßenoberbau genügen. Die Ursachen sind der hohe Anteil an Schluff- und Tonsteinen, aber auch die mangelnde Frostbeständigkeit der Sandsteine.Pit colliery shale is produced in drift mining in order to develop coal beds. Based on past investigations, a higher proportion of stable limestone material was expected in addition to the silty and clayey materials in pit colliery shale than is contained in the washed colliery shale from the coal beds. Because of the limestone material contained in pit colliery shale, the usability of pit colliery shale in unbound base courses was studied. The research included tests on the frost resistance, volume stability and the mechanical strength of the mineral aggregates which had been processed from pit colliery shale at two pilot facilities for possible use in road construction. The investigations revealed that neither the frost resistance nor the volume stability of pit colliery shale meets the requirements on mineral aggregates for pavement construction. The causes are not only the high contents of silty and clayey materials but also the poor frost resistance of the limestone material

Weathering resistance of recycled construction materials

Um die bisherigen Kenntnisse über die Verwitterungsbeständigkeit von Recycling-Baustoffen zu erweitern, wurde deren Widerstandsfähigkeit gegen Frost-Tau-Wechsel in verschiedenen Versuchsdurchführungen in Verbindung mit der Raumbeständigkeit und der Widerstandsfähigkeit gegen Schlag geprüft. Die Untersuchungen zeigten, dass zu den für bewährte Mineralstoffe geltenden Prüfungen zur Ermittlung der Widerstandsfähigkeit gegen Frost-Tau-Wechsel ergänzende Verfahren zugefügt werden müssen, um die Recyclingbaustoffe besser beurteilen zu können. So können mit einem Prüfverfahren, bei dem die Erhöhung des Feinkornanteils im Gemisch ermittelt wird, gute Aussagen gemacht werden. Es werden Aussagen zu Kennzeichnung, Festigkeit und Raumbeständigkeit der Recycling-Baustoffe gemacht und dazu Empfehlungen gegeben.In order to improve the previous knowledge about the weathering resistance of recycled construction materials, their susceptibility to the freezing-thaw cycle was studied in various tests in connection with their volume stability and impact resistance. The studies revealed that in order to improve the evaluation of recycled construction materials supplementary methods in addition to tests into the susceptibility to the freezing-thaw cycle traditionally used on accepted mineral aggregates are required. A method determining the increased content of fines in aggregates has proved to be a valuable evaluation instrument in this context. The report includes information on classification, material strength, and volume stability of recycled construction materials as well as recommendations concerning their use